Individuals who are wheelchair dependent generally need special cushioning to help prevent the formation of decubitus ulcers, which are often commonly referred to as pressure sores or bedsores. These individuals are often paralyzed and have lost sensation or have impaired sensation in their lower extremities. This loss or impairment of sensation presents problems associated with both bottoming-out in and the adjustment level of the cushion that the individual is sitting on. Bottoming-out raises the peak pressures on the skin in the bottomed-out areas of the individual to levels such that the blood flow in the capillary bed in the bottomed-out areas will be stopped (occluded) or reduced, which prevents vital nutrition from reaching the cells. This may cause necrosis or cell death and result in the onset of a decubitus ulcer. Improper adjustment or immersion can also result in decubitus formation.
Many variations of cushioning exist, including foam, gel, water-filled, air, foam and gel combinations, and air and foam combinations, etc. Cushioning to aid with pressure reduction must generally be adjusted to provide the proper fit for the shape of the user to distribute weight load on the skin to reduce pressures. These adjustments may involve sculpturing the foam to fit the contours of the person's body or adding special gel bags to a gel filled cushion. Air cushions generally require the checking of immersion depth by inserting one's hand under the buttocks. These adjustments may also include the checking of pressures with expensive computerized equipment. These adjustments are often specific and customized to the individual resulting in increased costs. Moreover, in nearly every instance where an individual shifts or adjust their seating posture, a new adjustment to the cushion may be required.
Conventional cushions have many disadvantages. Cushions may ultimately go out of adjustment or may deteriorate. Repeated use of a foam cushion may break down the cell structure of a foam cushion. Cushions may leak air or gel. Gel may become dry or become firm with the passage of time. Cushions may further change adjustment due to temperature or altitude changes.
If an individual lacks or has impaired sensation, they generally cannot detect that their cushion has failed to support their body properly. The individual may not be aware that a problem exists, until such time that a decubitus ulcer may have already formed. Even if aware of the fact that their cushion is bottomed out, misadjusted or has failed, many individuals cannot adjust their cushion by themselves due to their physical handicaps.